The present invention relates to apparent wind indicators for sailboats and, more particularly, to a wind indicating device which provides an indication of the proper orientation of the boat centerline to achieve optimum distance made good to or away from the windward direction.
In cruising and particularly in racing sailboats it is desirable to steer a course in which the greatest distance per unit of time toward or away from the windward direction is achieved. This will involve sailing either upwind or downwind, and in either case the centerline of the boat should be oriented at a particular angle with respect to the wind direction. This angle is generally dependent upon the upwind performance of the particular boat and the true wind velocity. Although it is recognized that there may be slight variation between boat centerline orientation and the actual course or line or progress, these terms are used interchangeable herein.
Optimum angles of boat centerline to apparent wind direction may be determined for typical boats at various wind velocities by known vector diagram constructions and mathematical calculations. Without going into further detail, it may be shown that in low wind velocities (e.g., 0-5 knots) the best sailing angle is on the order of 30.degree.; in moderate wind velocities (e.g., 6-10 knots), the angle should be about 20.degree.. In wind velocities greater than about 10 knots, the angle is again on the order of 30.degree..
Although the prior art includes devices for indicating apparent wind direction which are intended to aid in maintaining a desired course, such devices do not take into account the fact that optimum boat-to-wind angle varies with wind velocity. Other such devices, for example, that disclosed in U.S. Pat. No. 3,845,734, are designed to provide adjustment of sail trim, rather than boat direction, in accordance with apparent wind direction.
It is a principal object of the present invention to provide a visual indicating device for mounting on a sailboat to show the optimum alignment of the boat centerline at various wind velocities.
A further object is to provide a novel combined indicator of apparent wind direction and velocity which aids in establishing an optimum sailboat centerline orientation.
Another object is to provide a novel and improved device which visually indicates optimum boat-to-wind angles for sailboats of different pointing characteristics.
In a more general sense, the object of the invention is to provide a visual indicating device for use in establishing the course of a sailboat.
Other objects will in part be obvious and will in part appear hereinafter.